Cushion element for a patient interface

ABSTRACT

The present invention relates to a cushion element ( 14 ) for a patient interface ( 10 ) for providing a flow of breathable gas to a patient ( 12 ), wherein the cushion element ( 14 ) comprises a face-contacting layer ( 32 ) for contacting a face of the patient ( 12 ) during use of the cushion element ( 14 ) and a responsive layer ( 34 ) which is covered by the face-contacting layer ( 32 ). The responsive layer ( 34 ) comprises a plurality of active and passive zones ( 38, 40 ) that are arranged alternately side by side to one another. Each of the active zones ( 38 ) comprises at least one actuator ( 42 ) for moving the face-contacting layer ( 32 ), and wherein each of the passive zones ( 40 ) comprises a cushion material that is arranged between the actuators ( 42 ). The face-contacting layer ( 32 ) forms a corrugated or undulating surface ( 46 ) covering both the active and the passive zones ( 38, 40 ), wherein first parts ( 48 ) of said surface ( 46 ) covering the active zones ( 38 ) project beyond or are recessed relative to second parts ( 50 ) of said surface ( 46 ) covering the passive zones ( 40 ).

FIELD OF THE INVENTION

The present invention relates to a cushion element for a patientinterface for providing a flow of breathable gas to a patient. Thepresent invention particularly relates to a cushion element that isimproved with respect to a more efficient prevention of a formation ofred marks within the face of the patient. Still further, the presentinvention relates to a patient interface and a pressure support systemwhich make use of such a cushion element.

BACKGROUND OF THE INVENTION

Patient interfaces, such as masks for covering the mouth and/or nose,are used for delivering gas to a patient. Such gases, like air, cleanedair, oxygen, or any modification of the latter, are submitted to thepatient via the patient interface in a pressurized or unpressurized way.

For several chronic disorders and diseases, a long-term attachment ofsuch a patient interface to a patient is necessary or at leastadvisable.

One non-limiting example for such a disease is obstructive sleep apneaor obstructive sleep apnea syndrome (OSA). OSA is usually caused by anobstruction of the upper airway. It is characterized by repetitivepauses in breathing during sleep and is usually associated with areduction in blood oxygen saturation. These pauses in breathing, calledapneas, typically last 20 to 40 seconds. The obstruction of the upperairway is usually caused by a reduced muscle tonus of the body thatoccurs during sleep. The human airway is composed of walls of softtissue which can collapse and thereby obstruct breathing during sleep.Tongue tissue moves towards the back of the throat during sleep andthereby blocks the air passages. OSA is therefore commonly accompaniedwith snoring.

Different invasive and non-invasive treatments for OSA are known. One ofthe most powerful non-invasive treatments is the usage of ContinuousPositive Airway Pressure (CPAP) or Bi-Positive Airway Pressure (BiPAP)in which a patient interface is connected to a pressure generator via apatient circuit including one or more tubes, wherein the pressuregenerator blows pressurized gas into the patient interface and into thepatient's airway in order to keep it open. Positive air pressure is thusprovided to a patient by means of the patient interface that is worn bythe patient typically during sleep.

Examples for such patient interfaces are:

nasal masks, which fit over the nose and deliver gas through the nasalpassages,

oral masks, which fit over the mouth and deliver gas through the mouth,

full-face masks, which fit over both the nose and the mouth and delivergas to both, and

nasal pillows, which are regarded as patient interfaces as well withinthe scope of the present invention and which consist of small nasalinserts that deliver gas directly to the nasal passages.

The patient interface is usually positioned and donned to the patient'shead using some kind of headgear. Further, the patient interface maycomprise a forehead support. Such a forehead support is often designedas a pad that touches the forehead of a patient during use. It is oftenincluded in order to relief the pressure which the patient interfaceexerts onto the nose bridge.

Wearing a patient interface can be uncomfortable, since for providing anairtight seal between the patient interface and the patient's face, thepatient interface has to be worn with a sufficient level of pressure onthe face. It is thus evident that users of the patient interfacesexperience a lot of disadvantages, wherein the most prominentdisadvantage is the formation of facial red marks after a long-termusage of the patient interface. These red marks result from occlusionsof blood vessels which arise from the pressure exerted by the patientinterface.

A promising concept for preventing uncomfortable pressure points, redmarks, indentations, and overall prolonged discomfort is the use ofcushion elements that provide an alternating pressure onto the skin ofthe patient. This restores the skin blood flow in the depressurized partof the cushion element. One approach for providing cushion elements withan alternating pressure distribution is the use of electroactivepolymers (EAPs) within the cushion elements. Dielectric elastomeractuators (DEAs) are smart material systems which produce large strains(up to 300%) and belong to the group of EAPs. Based on their simpleworking principle DEAs transform electric energy directly intomechanical work. DEAs are lightweight and free shapeable.

A DEA is a thin and flexible electroactive polymer sheet enclosedbetween two compliant electrodes. The thickness of the electroactivepolymer sheet is controlled by the applied electrode voltage.Correspondingly, a thickness change results in elongation change. Soboth the thickness as well as the elongation of the sheet can becontrolled. If applied to the skin, the alternating dimensions willimpose an alternating pressure or stretch to the skin.

An example for a cushion element that includes EAP-actuators is knownfrom WO 2013/183018 A1. The EAP-actuators used therein continuouslyalter the skin pressure distribution, provide a slow massaging motion tothe skin, and relieve high local pressure peaks.

However, there is still room for improvement. One of the main technicalchallenges is the technical design and arrangement of such actuatorswithin the cushion element. It is particularly challenging to design andarrange the actuators in such a way that static pressure points may beeffectively avoided.

A typical way to produce an EAP actuator is to spin coat or blade thepolymer layer and to spray coat or paint the compliant electrode. Thereis a need to segment the electrodes so that alternating pressure(switching from segment A to segment B) can be realized. However, theseelectrode-segments are placed at a certain distance away from each otherin order to prevent electric arcing from one electrode to the other. Thegap between the electrode-segments is usually in the range of 1-2 mm andminimally in the range of 200-500 μm. This gap can be responsible forstatic pressure points on the cushion element, which can lead to redmarks.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide an improved cushionelement for a patient interface, wherein the cushion element moreeffectively overcomes the problem of a red mark formation due to staticpressure points on or within the cushion element. It is especially anobject of the present invention to provide a cushion element includingone or more actuators for providing an alternating pressure distributionwithin the cushion element, wherein the technical design and thearrangement of the actuators within the cushion element is improved.

According to an aspect of the present invention, a cushion element for apatient interface for providing a flow of breathable gas to a patient ispresented, wherein the cushion element comprises:

a face-contacting layer for contacting a face of the patient during useof the cushion element; and

a responsive layer which is covered by the face-contacting layer;

wherein the responsive layer comprises a plurality of active and passivezones that are arranged alternately side by side to one another,

wherein each of the active zones comprises at least one actuator formoving the face-contacting layer, and wherein each of the passive zonescomprises a cushion material that is arranged between the actuators,

wherein the face-contacting layer forms a corrugated or undulatingsurface covering both the active and the passive zones, wherein firstparts of said surface covering the active zones project beyond or arerecessed relative to second parts of said surface covering the passivezones.

According to a further aspect of the present invention, a patientinterface comprising a cushion element of the above-mentioned type ispresented.

According to still further aspect of the present invention, a pressuresupport system is presented which comprise a pressure generator forgenerating a flow of breathable gas, and a patient interface forproviding the flow of breathable gas to a patient, wherein the patientinterface comprises a cushion element of the above-mentioned type.

Preferred embodiments of the invention are defined in the dependentclaims. It shall be understood that the claimed patient interface andthe claimed pressure support system have similar and/or identicalpreferred embodiments as the claimed cushion element and as defined inthe dependent claims.

The herein presented cushion element comprises a plurality of actuatorswhich are configured to move the face-contacting layer of the cushionelement in a predefined movement pattern in order to prevent a formationof red marks within the face of the patient. In contrast to prior artcushion elements of this type, the herein presented cushion elementprovides an improved arrangement of the actuators as well as an improvedtechnical design of the cushion element itself.

The cushion element comprises a face-contacting layer which isconfigured to contact the face of the patient during use of the cushionelement. This face-contacting layer builds the top surface of thecushion element. The face-contacting layer is preferably realized as acontinuous layer that (fully) covers a responsive layer which isarranged below. The responsive layer is divided into so-called activeand passive zones. However, it shall be noted that the terms “active”and “passive” shall not be considered to be limiting or to imply anyspecial meaning other than the following. The active zones of theresponsive layer are zones or areas in which at least one actuator isarranged. The passive zones are zones or areas in which a cushionmaterial is arranged but no actuator. The active and passive zones couldalternatively also be denoted as first and second zones. It shall befurthermore noted that the term “a plurality of” shall mean “at leasttwo”.

It is important that the active and passive zones are arrangedalternately side by side to one another. This means that each activezone is sandwiched between two neighbouring passive zones, and eachpassive zone (except the passive zones arranged at the border of thecushion element) is sandwiched between two neighbouring active zones.

Since the actuators for moving the face-contacting layer are onlyarranged in the active zones, an actuation of the actuators will cause adirect movement of the active zones and the parts (herein denoted as“first parts”) of the face-contacting layer covering and contacting theactive zones. However, since the passive zones are sandwiched in betweenthe active zones, an actuation of the actuators at least indirectly alsocauses a movement of the passive zones of the responsive layer and theparts (herein denoted as “second parts”) of the face-contacting layercovering and contacting the passive zones. This indirect movement of thepassive zones arises from the fact that cushion material, which may bepresent in the active zones between the electrodes of the actuators, istransferred to and from the passive zones due to material movement assoon as the actuators deform the active zones of the cushion element. Itis therefore preferred that the cushion material comprises a pliable,resilient and/or elastic material that is deformable under pressure.Typical materials of this type are elastomers, like silicon, acrylics orpolyurethane.

The one or more actuators that are arranged in each of the active zonesof the cushion element are preferably configured to move theface-contacting layer in a periodic manner.

A further characterizing feature of the herein presented cushion elementis the shape of the face-contacting layer. The face-contacting layerforms a corrugated or undulating surface which covers both the activeand the passive zones. The first parts of said corrugated or undulatingsurface cover and contact the active zones, and the second parts of saidcorrugated and undulating surface cover and contact the passive zones ofthe responsive layer. The first and second parts of said surface arethus also arranged alternately side by side to one another (similar asthe active and passive zones of the responsive layer). The first partspreferably also contact the neighbouring second parts, such that thecorrugated or undulating surface is a continuously connected surface.The term “corrugated or undulating surface” shall mean that said surfaceis an uneven surface having elevations/bumps and recesses. The firstparts of said surface, which cover the active zones, project beyond orare recessed relative to the second parts of said surface, which coverthe passive zones. An activation of the actuators thus causes anundulating or wavelike movement of the face-contacting layer. Thisundulating or wavelike movement may be, but does not necessarily have tobe a periodic movement. This movement prevents static pressure pointsand provides a smooth massaging effect in the face of the patient.

It shall be noted that the elevations and recesses of theface-contacting layer are not restricted to any special shape of theircross-sections. The elevations and recesses of the face-contacting layermay have any shape, like a cubical, rectangular, round, conical orelliptical shape.

According to an embodiment of the present invention, the actuators areconfigured to move the first parts of the corrugated or undulatingsurface relative to the second parts of said surface by expanding theactive zones in a first direction towards the face of the patient and/orby contracting the active zones in a direction opposite the firstdirection. Thus, fairly simple and cost-saving actuators may be usedwhich either contract or expand the cushion material within the activezones upon activation. The first direction is preferably meant to denotea direction transverse or perpendicular to the interface between thecushion element and the patient's face during use.

The active zones are preferably configured to communicate with thepassive zones via the cushion material that is integrated in theresponsive layer, such that an expansion of the active zones causes acontraction of the passive zones, and a contraction of the active zonescauses an expansion of the passive zones. Depending on the movement ofthe active zones the cushion material is thus pushed from the activezones into the neighbouring passive zones or vice versa. If theactuators contract the active zones upon activation of the actuators,the cushion material present in the active zones in between theactuators will be pushed into the neighbouring passive zones. This willautomatically cause the second parts of the face-contacting layercovering the passive zones to bulge outwardly towards the patient'sface, whereas the first parts of the face-contacting layer covering theactive zones will be pulled-in at the same time. A deactivation of theactuators would in this case cause the active zones to expand again,such that the cushion material will be pulled in the active zones fromthe neighbouring passive zones. This will cause the first parts of theface-contacting layer to bulge outwardly towards the patient's face,whereas the second parts of said layer will be pulled in. A periodicactivation and deactivation of the actuators thus causes the corrugatedor undulating surface of the face-contacting layer to move in anundulating or wave-like manner. The pressure points where theface-contacting layer touches the skin of the patient so to say switchplaces during this movement of the cushion element. The cushion elementwill alternately contact the patient's face with the first parts and thesecond parts of the face-contacting layer.

According to an embodiment, the active and passive zones are arranged incolumns next to one another, wherein columns forming the active zonesand columns forming the passive zones are arranged alternately side byside to one another. The columns forming the active zones and thecolumns forming the passive zones are preferably arranged parallel toone another and parallel to the first direction. It shall be noted againthat this first direction denotes the direction of the movement of theactive zones towards the patient's face, which movement is caused by theactuators. A parallel arrangement of the active and passive zonesfurthermore has the advantage that the switching pressure points areequally distributed over the cushion element. This results in awell-controllable and comfortable massaging effect of the patient's skinthat prevents a formation of red marks. Leakages occurring at theinterface between the patient's face and the cushion element are alsoprevented, since it is ensured that either the first parts or the secondparts of the corrugated or undulating surface contact the skin andthereby provide a sufficient seal.

According to a further embodiment, the cushion element additionallycomprises a support layer for providing mechanical stability to theresponsive layer, wherein the support layer is arranged on a first sideof the responsive layer, and wherein the face-contacting layer isarranged on a second side opposite the first side of the responsivelayer. The responsive layer is in this embodiment thus sandwichedbetween the support layer and the face-contacting layer. It isespecially preferred that each of the active zones and each of thepassive zones contact the responsive layer with their first side and theface-contacting layer with their second side.

The additional support layer is preferably configured to be stiffer orless resilient than the face-contacting layer and/or the responsivelayer of the cushion element. In this way it is ensured that themovement of the actuators is mainly translated into a movement of theface-contacting layer and not into a movement of the support layer.

According to a further embodiment, the at least one actuator of eachactive zone comprises an electroactive polymer and an electrode foractivating the electroactive polymer. The electroactive polymer materialmay be the same as the before-mentioned cushion material. By the help ofsuch electroactive polymer materials, electric energy may be directlytransformed into mechanical work. Electroactive polymers provide theadvantage that they are lightweight and free shapeable. By applying analternating voltage to the electrodes the electroactive polymer materialmay be forced to expand and contract alternatingly. Examples of suchelectroactive polymer materials are: piezoelectric polymers,electromechanical polymers, relaxor ferroelectric polymers,electrostrictive polymers, dielectric elastomers, liquid crystalelastomers, conjugated polymers, Ionic Polymer Metal Composites, ionicgels, and polymer gels.

Even though the usage of such EAP actuators is preferred according tothe present invention, the above-mentioned actuation and movementprinciple may also be accomplished with other types of actuators.Instead of EAPs, light-activated materials could e.g. be used as well.Other responsive materials, which could be used as actuators for thepresent invention, are: electroactive composites, electrostrictiveceramics or crystals, shape memory polymers, photomechanical materials,magnetostrictive materials, chemomechanical materials, and bimetalcomposites.

In order to amplify the movement of the face-contacting layer whilestill being able to use relatively low voltages (low energy), it isespecially preferred that each of the active zones comprises a pluralityof actuators. In case of the use of EAP actuators it is preferred thateach of the plurality of actuators comprises an electroactive polymerand an electrode that is arranged transverse to the first direction. Theelectrodes are thus arranged above each other, wherein the gaps betweenthe electrodes are filled up with the electroactive polymer material(the cushion material). Some electrodes may belong to two neighbouringactuators, whereas actuators arranged at the borders of the active zonesbelong to only one actuator. The plurality of actuators in each activezone may also be referred to as one common actuator arrangement.

According to a further embodiment, each of the active zones has a width(w) of 100 μm≦w≦100 mm, said width (w) being measured in a seconddirection transverse to the first direction. Said width dimensions ofthe active zones ensure a large enough but not too large movement of thefirst parts of the corrugated or undulating surface.

According to a further embodiment, the active zones are arranged inconcentric closed loops. Such an arrangement is especially preferred ifthe cushion element is realized as a nose cushion or a mouth cushion.The passive zones will then similarly be arranged in concentric closedloops sandwiched between the active zones. This provides the advantagethat even though the face-contacting layer alternatingly moves in theabove-mentioned way during use, no pressure leakages occur, as theactive and passive zones so to say fully surround the nose and/or themouth of the patient. However, it shall be noted that such anarrangement is not necessarily needed if the cushion element is realizedas a cushion or pad of a forehead support of the patient interface. Suchforehead cushions usually do not have to form a seal.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other aspects of the invention will be apparent from andelucidated with reference to the embodiment described hereinafter. Inthe following drawings

FIG. 1 shows an exemplary embodiment of a patient interface in which acushion element according to the present invention may be applied;

FIG. 2 shows a backside of the patient interface shown in FIG. 1; and

FIG. 3 shows a schematic cross section of an embodiment of the cushionelement according to the present invention, wherein FIG. 3A shows thecushion element in a first operating state and FIG. 3B shows the cushionelement in a second operating state.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows an exemplary embodiment of a patient interface fordelivering a flow of breathable gas to a patient. The patient interfaceis therein in its entirety denoted by reference numeral 10.

In this embodiment the patient interface 10 is designed as a full-facemask covering the mouth and the nose of a patient 12. It shall be notedthat the patient interface 10 may alternatively be designed as a nosemask, a mouth mask or as a total face mask without leaving the scope ofthe present invention.

The patient interface 10 comprises a cushion element 14 and a mask shell16. The cushion element 14 is designed to contact the face of thepatient 12 and to provide an airtight seal at the interface between thepatient's face and the patient interface 10. The cushion element 14usually comprises a soft material, like silicon or any other rubber orsuitable elastic material. The mask shell 16 provides a flexible,semi-rigid or rigid support structure for holding the cushion element14. The mask shell 16 is usually connected to the backside of thecushion element 14, wherein the backside is meant to denote the side ofthe cushion element 14 opposite to the side of the cushion element 14contacting the patient's face during use. The mask shell 16 may eitherbe releasably or fixedly connected to the cushion element 14. Thecushion element 14 and the mask shell 16 thus together form a cavitywhich is in this case designed to receive the mouth and the nose of thepatient 12. It shall be noted that the cushion element 14 and the maskshell 16 may alternatively be formed as one integral piece.

On the opposite side directing away from the patient's face, the maskshell 16 preferably comprises a connector 18. Via this connector 18 thepatient interface 10 may be connected to a hose (not shown) via which apressurized flow of breathable gas can be submitted to the patientinterface 10. The mask shell 16 is further connected to a headgear 20.This headgear 20 is used for attaching the patient interface 10 to thepatient's head. According to the exemplary embodiment shown in FIG. 1,the headgear 20 comprises a rigid frame 22 and lower and upper headgearstraps 24, 26. These lower and upper headgear straps 24, 26 may beconnected to the frame 22 of the headgear 20 and used for donning themask shell 16 and the cushion element 14 to the patient's face.

In the illustrated example the headgear 20 furthermore comprises aforehead support 28. This forehead support 28 allows stabilizing thepatient interface 10 while being donned to the patient's face. Theforehead support 28 reduces the pressure that is exerted onto thepatient's nose during use. In order to make the forehead support 28 ascomfortable as possible, the forehead support 28 furthermore comprises aforehead cushion 30 which is attached thereto. This forehead cushion 30is according to the present invention also considered as a cushionelement (similar as cushion element 14).

FIG. 2 shows a schematic view of the patient interface 10, the cushionelement 14 and the forehead support 28 from the other side, i.e. fromthe side with which the cushion element 14 and the forehead cushion 30contact the patient's face.

FIGS. 3A and 3B show a schematic cross section of the cushion element 14according to an embodiment of the present invention. The multi-layerstructure of the cushion element 14 is therein illustrated in detail.

In the illustrated example the cushion element 14 basically comprisesthree layers: a face-contacting layer 32, a responsive layer 34 and asupport layer 36. The face-contacting layer 32 forms the top surface ofthe cushion element 14 that contacts the patient's face during use. Itmay be made of a thin elastomeric film and has the function to provide askin-friendly interface. The support layer 36 is arranged at thebackside of the cushion element 14 that is usually connected to the maskshell 16. This support layer 36 is preferably made of a rubber materialthat is stiffer and less resilient than the materials from which theface-contacting layer 32 and the responsive layer 34 are made. Thesupport layer 36 shall provide mechanical stability. However, it shallbe noted that this support layer 36 is not necessarily needed if thefunction of providing mechanical stability is fulfilled by the maskshell 16 itself. The responsive layer 34 would in this case besandwiched between the face-contacting layer 32 and the mask shell 16instead of being sandwiched between the face-contacting layer 32 and thesupport layer 36 as shown in FIG. 3. Both alternatives are possible.

One of the central features of the presented cushion element 14 is thestructure of the responsive layer 34. The responsive layer 34 is splitup into active zones/areas 38 and passive zones/areas 40. Zones 38 arecalled active zones since these zones of the responsive layer 34 areconfigured to actively move the face-contacting layer 32. Zones 40 aredenoted as passive zones since these zones are not actively moved(actuated), but move indirectly as soon as the active zones 38 aremoved. This will become more apparent from the explanations given below.

As it can be seen in FIGS. 3A and 3B, the active zones 38 and thepassive zones 40 are arranged alternately side by side to one another.The active and passive zones 38, 40 are in the shown example arranged inparallel columns next to one another. Each active zone 38 comprises aplurality of actuators 42. These actuators 42 are configured to move theface-contacting layer 32 by expanding the active zones 38 in a firstdirection 44 towards the patient's face and/or by contracting the activezones 38 in a direction opposite the first direction 44. The actuators42 are preferably configured to periodically expand and contract theactive zones 38 of the responsive layer 34. In order to realize thismovement the use of electrically actuated actuators 42 is preferred.Such actuators 42 may, for example, be controlled in such a way that theactive zones 38 are contracted when the actuators 42 are activated,whereas the active zones 38 are expanded again when the actuators 42 aredeactivated. However, it is also possible to control such actuators 42the other way around, such that, they expand the active zones 38 whenbeing activated and contract the active zones 38 again when beingdeactivated. A preferred embodiment for such actuators 42 will beexplained further below.

A further central feature of the cushion element 14 according to thepresent invention is the technical design and structure of theface-contacting layer 32. In contrast to most cushion elements 14according to the prior art, this face-contacting layer 32 is not formedas an even, flat surface, but rather formed as an uneven, corrugated orundulating surface 46 (see FIGS. 3A and 3B). This surface 46 comprisesseveral interconnected segments which are herein denoted as first parts48 and second parts 50 of the surface 46. The first parts 48 are theparts of the corrugated or undulating surface 46 that cover the activezones 38. The second parts 50 are the parts of the surface 46 that coverthe passive zones 40. The first and second parts 48, 50 are thereforealso arranged alternately side by side to one another. Depending on theactivation state of the actuators 42, the first parts 48 of the surface46 either project beyond or are recessed relative to the second parts 50of the surface 46. In the exemplary embodiment shown in FIG. 3, FIG. 3Ashows the deactivated state of the actuators 42 and FIG. 3B shows theactivated state of the actuators 42. In this example, the first parts 48thus project beyond the second parts 50 in the deactivated state (seeFIG. 3A), whereas the first parts 48 are recessed relative to the secondparts 50 in the activated state of the actuators 42 (see FIG. 3B). It isclear that the technical design may be chosen to be just the way around.

Due to the above-mentioned structure of the cushion element 14, theface-contacting layer 32 does not contact the patient's face along thewhole surface 46 during use, but rather performs an undulating orwavelike movement. This prevents static pressure points which couldotherwise lead to a formation of red marks within the patient's face.

In the preferred embodiment illustrated in FIGS. 3A and 3B the actuators42 are designed as electroactive polymer (EAP) actuators. In this caseeach EAP actuator 42 comprises two opposing electrodes 52 and anelectroactive polymer material 54 that is arranged in between theelectrodes 52. The electroactive polymer material 54 may be eitherconfigured to contract or to expand as soon as a voltage is applied tothe electrodes 52. In the shown example, the electroactive polymermaterial 54 is configured to contract as soon as a voltage is appliedthereto

It can be furthermore seen from FIGS. 3A and 3B that each active zone 38of the responsive layer 34 comprises a plurality of electrodes 52 andelectroactive polymer layers 54 arranged in between them. The electrodes52 are preferably arranged perpendicular to the first direction 44, i.e.parallel to the first parts 48 of the undulating surface 46.

FIG. 3B shows the activated state of the actuators 42, i.e. the state inwhich a voltage is applied to the electrodes 52. By comparing FIG. 3Awith FIG. 3B it may be seen that the first parts 48 of the undulatingsurface 46 so to say change places with the second parts 50 of theundulating surface 46 as soon as a voltage is applied to the electrodes52 of the actuators 42. This results from the following fact: The activezones 38 communicate with the passive zones 40 via the cushion materialthat is integrated in the responsive layer 34. An activation of theactuators 42 causes the active zones 38 to contract (see FIG. 3B). Thiscontraction shifts the material, which is present in between theelectrodes 52, from the active zones 38 into the passive zones 40. Thesecond parts 50 of the undulating surface 46 will then bulge outwardlyso that they then project beyond the first parts 48 of the undulating46. A wavelike movement of the face-contacting layer 32 may thus beachieved by alternately activating and deactivating the actuators 42 inthe active zones 38 of the responsive layer 34. During this movement thefirst parts 48 and the second parts 50 of surface 46 will be alternatelyin contact with the patient's face.

The actuators 42 of the above-mentioned exemplary embodiment may beeasily driven by a voltage source (e.g. a battery) which is eitherintegrated into the cushion element 14 itself or arranged at anotherposition on the patient interface 10. This voltage source (not shown) ispreferably connected to each of the actuators 42 via a voltageconverter. A simple microprocessor may be used to steer the actuators 42in the above-mentioned way.

The width w of the active and passive zones 38, 40 may be designed in arelatively free manner. Experiments of the applicant have shown that thebest massaging effects may be achieved if the width w ranges between 100μm and 100 mm.

It shall be further noted that the above-mentioned structure of thecushion element 14 may not only be used in the main cushion 14 formingthe airtight seal of the mask 10, but could alternatively oradditionally also be used in the forehead cushion 30. The onlydifference is that in the sealing cushion 14 one also needs to takeaccount for the sealing behavior such a cushion element should fulfill.It is therefore preferred that the active zones 38 and passive zones 40of the responsive layer 34 are arranged in concentric closed loops (seeFIG. 2).

While the invention has been illustrated and described in detail in thedrawings and foregoing description, such illustration and descriptionare to be considered illustrative or exemplary and not restrictive; theinvention is not limited to the disclosed embodiments. Other variationsto the disclosed embodiments can be understood and effected by thoseskilled in the art in practicing the claimed invention, from a study ofthe drawings, the disclosure, and the appended claims.

In the claims, the word “comprising” does not exclude other elements orsteps, and the indefinite article “a” or “an” does not exclude aplurality. A single element or other unit may fulfill the functions ofseveral items recited in the claims. The mere fact that certain measuresare recited in mutually different dependent claims does not indicatethat a combination of these measures cannot be used to advantage.

Any reference signs in the claims should not be construed as limitingthe scope.

1. A cushion element for a patient interface for providing a flow ofbreathable gas to a patient, wherein the cushion element comprises: aface-contacting layer for contacting a face of the patient during use ofthe cushion element; and a responsive layer which is covered by theface-contacting layer; wherein the responsive layer comprises aplurality of active and passive zones that are arranged alternately sideby side to one another, wherein each of the active zones comprises atleast one actuator for moving the face-contacting layer, and whereineach of the passive zones comprises a cushion material that is arrangedbetween the actuators, wherein the face-contacting layer forms acorrugated or undulating surface covering both the active and thepassive zones, wherein first parts of said surface covering the activezones project beyond or are recessed relative to second parts of saidsurface covering the passive zones.
 2. The cushion element according toclaim 1, wherein the actuators are configured to move the first parts ofsaid surface relative to the second parts of said surface by expandingthe active zones in a first direction towards the face of the patientand/or by contracting the active zones in a direction opposite the firstdirection.
 3. The cushion element according to claim 2, wherein theactive zones are configured to communicate with the passive zones viathe cushion material that is integrated in the responsive layer, suchthat an expansion of the active zones causes a contraction of thepassive zones, and a contraction of the active zones causes an expansionof the passive zones.
 4. The cushion element according to claim 1,wherein the active and passive zones are arranged in columns next to oneanother, wherein columns forming the active zones and columns formingthe passive zones are arranged alternately side by side to one another.5. The cushion element according to claim 2, wherein the columns formingthe active zones and the columns forming the passive zones are arrangedparallel to the first direction.
 6. The cushion element according toclaim 1, further comprising a support layer for providing mechanicalstability to the responsive layer, wherein the support layer is arrangedon a first side of the responsive layer, and wherein the face-contactinglayer is arranged on a second side opposite the first side of theresponsive layer.
 7. The cushion element according to claim 1, whereinthe at least one actuator of each active zone comprises an electroactivepolymer and an electrode for activating the electroactive polymer. 8.The cushion element according to claim 1, wherein each of the activezones comprises a plurality of actuators.
 9. The cushion elementaccording to claim 2, wherein each of the plurality of actuatorscomprises an electroactive polymer and an electrode that is arrangedtransverse to the first direction.
 10. The cushion element according toclaim 2, wherein each of the active zones has a width (w) of 100μm≦w≦100 mm, said width (w) being measured in a second directiontransverse to the first direction.
 11. The cushion element according toclaim 1, wherein the plurality of active zones are arranged inconcentric closed loops.
 12. The cushion element according to claim 1,wherein the cushion element is one of a nose cushion, a mouth cushionand a forehead cushion.
 13. A patient interface for providing a flow ofbreathable gas to a patient, wherein the patient interface comprises acushion element according to claim
 1. 14. The patient interfaceaccording to claim 13, further comprising a voltage source which isconnected to the at least one actuator of each active zone.
 15. Apressure support system, comprising: a pressure generator for generatinga flow of breathable gas; and a patient interface for providing the flowof breathable gas to a patient, wherein the patient interface comprisesa cushion element according to claim 1.